Board assembly sheet

ABSTRACT

A board assembly sheet includes a plurality of mounting boards each for mounting an electronic component. The mounting boards are defined in the board assembly sheet. The mounting board has a total thickness of 60 μm or less. The board assembly sheet has a through hole passing through the board assembly sheet in a thickness direction. The through hole is formed to be along an end edge of the mounting board or along a phantom line extending along the end edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. 371 National Stage Entry ofPCT/JP2018/036795, filed on Oct. 2, 2018, which claims priority fromJapanese Patent Application No. 2017-207356, filed on Oct. 26, 2017, thecontents of all of which are herein incorporated by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a board assembly sheet.

BACKGROUND ART

Conventionally, an imaging device such as camera module mounted on acellular phone or the like has been generally mounted with an opticallens, a housing that houses and retains the optical lens, an imagingelement such as CMOS sensor and CCD sensor, and an imagingelement-mounting board that is mounted with the imaging element forbeing electrically connected to an external wire. The imaging element ismounted on a generally central portion of the imaging element-mountingboard, and the housing is disposed on a peripheral end portion of theimaging element-mounting board so as to surround the imaging element.Patent Document 1 discloses the board.

CITATION LIST Patent Document

Patent Document 1: Japanese Unexamined Patent Publication No.2005-210628

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The imaging device used in the cellular phone or the like is required tofurther reduce its thickness (height) along with a demand for a smallercellular phone. As one of the methods of reducing the height of theimaging device, a reduction in thickness of the imaging element-mountingboard has been considered.

Generally, in the imaging element-mounting board, two types of a thickrigid-type wiring circuit board that reinforces the entire rear surfacethereof with a metal plate, and a thin flexible-type wiring circuitboard (FPC) that does not reinforce the entire rear surface thereof withthe metal plate are used.

The FPC is not reinforced with the metal plate, so that a reduction inthickness thereof is possible compared to the rigid-type wiring circuitboard. However, on the other hand, materials for the imaging element andthe imaging element-mounting board are different from each other, sothat when an imaging unit including the imaging element and the imagingelement-mounting board is placed under the external environment where ahigh temperature and a low temperature are repeated, thermal distortionmay be generated to cause warping of the imaging unit. As a result,there is a disadvantage that a deviation is generated in the position ofthe imaging element and the optical lens, so that an image is distorted.

Then, the use of an ITC having a significantly thin total thickness hasbeen considered. Such an FPC has a significantly reduced thermal stress,so that generation of the warping can be suppressed.

However, the above-described FPC is thin and thus, easily broken. Thereis a disadvantage that, especially in view of mass production, the FPCboard assembly sheet is broken when an FPC board assembly sheet having aplurality of FPCs is fabricated and next, the plurality of FPCs aresingulated from the FPC assembly by a dicing blade. As a result, a yieldis reduced.

The present invention provides a board assembly sheet that is capable ofefficiently obtaining a plurality of mounting boards.

Means for Solving the Problem

The present invention [1] includes a board assembly sheet including aplurality of mounting boards each for mounting an electronic component,the mounting boards being defined in the board assembly sheet, whereinthe mounting board has a total thickness of 60 μm or less, the boardassembly sheet has a through hole passing through the board assemblysheet in a thickness direction, and the through hole is formed to bealong an end edge of the mounting board or along a phantom lineextending along the end edge.

According to the board assembly sheet, the through hole is formed to bealong the end edge of the mounting board or along the phantom line.Thus, the dicing blade is inserted into the through hole, and the boardassembly sheet can be cut from the side end edge thereof along themounting board end edge or along the phantom line. Thus, when the dicingblade is brought into contact with the board assembly sheet, an impactor a distortion (deformation) imparted to the entire board assemblysheet can be reduced. Therefore, damage of the board assembly sheet andaccordingly, the damage of the mounting board formed therein can bereduced at the time of singulation, and the yield of the mounting boardcan be improved. That is, the plurality of mounting boards can beefficiently obtained.

In addition, the through hole is formed in advance, so that cuttingdusts generated by cutting can be reduced, and contamination of themounting board can be suppressed.

The present invention [2] includes the board assembly sheet described in[1], wherein the mounting board has a generally rectangular shape whenviewed from the top extending in a first direction and a seconddirection perpendicular to the first direction, and the through holeincludes a first through hole extending in the first direction and asecond through hole extending in the second direction.

According to the board assembly sheet, the first through hole extendingin the first direction and the second through hole extending in thesecond direction are included, so that the impact or the distortionimparted to the entire board assembly sheet can be reduced at the timeof cutting in the first direction and the second direction. Thus, themounting board in a generally rectangular shape when viewed from the topcan be more surely obtained without damage.

The present invention [3] includes the board assembly sheet described in[1] or [2], wherein a length of the through hole in an orthogonaldirection perpendicular to a direction along the end edge is 2000 μm orless.

According to the board assembly sheet, when the board assembly sheet iscut by using a dicing blade having the same width as the length of thethrough hole in the orthogonal direction, the cutting area can bereduced. Thus, the cutting dusts can be reduced, and the contaminationof the mounting board can be suppressed.

The present invention [4] includes the board assembly sheet described in[3], wherein the length of the through hole in the orthogonal directionis generally the same as a distance between two mounting boards next toeach other in the orthogonal direction.

According to the board assembly sheet, the end edge of one mountingboard and the end edge of the other mounting board can be cut by onecutting. Thus, there is no need for cutting in each of the end edges, sothat the number of cutting steps can be reduced.

The present invention [5] includes the board assembly sheet described inany one of [1] to [4], wherein the through hole has end edges facingeach other in a direction along the end edge gradually get closer toeach other in the thickness direction.

According to the board assembly sheet, both end edges of the throughhole have a shape of gradually getting closer to each other in thethickness direction, so that the dicing blade can be gradually broughtinto contact with the end edge of the through hole to be cut. Thus, theimpact imparted to the entire board assembly sheet can be furthermorereduced, and the damage of the board assembly sheet can be furthermoresuppressed.

The present invention [6] includes the board assembly sheet described inany one of [1] to [5], wherein the through hole is formed between twomounting boards next to each other.

According to the board assembly sheet, the through hole is formed inadvance around the mounting board, so that adhesion of the cutting duststo the mounting board can be furthermore suppressed at the time ofcutting.

Effect of the Invention

The board assembly sheet of the present invention allow the plurality ofmounting boards to be obtained efficiently, while suppressing the damageof the mounting board. In addition, the cutting dusts generated by thecutting can be reduced, and the contamination of the mounting board canbe suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a first embodiment of a board assembly sheetof the present invention.

FIGS. 2A to 2B show cross-sectional views of the board assembly sheetshown in FIG. 1:

FIG. 2A illustrating an A-A cross-sectional view and

FIG. 2B illustrating a B-B cross-sectional view.

FIGS. 3A to 3F show production process views and a cutting process viewof the board assembly sheet shown in FIG. 1:

FIG. 3A illustrating a metal supporting plate preparing step,

FIG. 3B illustrating a base insulating layer forming step,

FIG. 3C illustrating a conductive pattern forming step,

FIG. 3D illustrating a cover insulating layer forming step,

FIG. 3E illustrating a metal supporting plate removing step, and

FIG. 3F illustrating a cutting step.

FIG. 4 shows a plan view of a board assembly sheet after cutting.

FIG. 5 shows an imaging device including a mounting board obtained fromthe board assembly sheet shown in FIG. 1.

FIG. 6 shows a plan view of a modified example (embodiment including areinforcement layer) of the board assembly sheet shown in FIG. 1.

FIG. 7 shows an A-A cross-sectional view of the board assembly sheetshown in FIG. 6.

FIG. 8 shows a plan view of a modified example (embodiment in which theboard assembly sheet is a long-length sheet) of the board assembly sheetshown in FIG. 1.

FIG. 9 shows a plan view of a second embodiment of a board assemblysheet of the present invention.

FIG. 10 shows a plan view of a third embodiment of a board assemblysheet of the present invention.

FIG. 11 shows a plan view of a fourth embodiment of a board assemblysheet of the present invention.

FIG. 12 shows an A-A cross-sectional view of the board assembly sheetshown in FIG. 11.

DESCRIPTION OF EMBODIMENTS

In FIG. 1, the up-down direction on the plane of the sheet is afront-rear direction (first direction), the lower side on the plane ofthe sheet is a front side (one side in the first direction), and theupper side on the plane of the sheet is a rear side (the other side inthe first direction). The right-left direction on the plane of the sheetis a right-left direction (second direction perpendicular to the firstdirection), the left side on the plane of the sheet is a left side (oneside in the second direction), and the right side on the plane of thesheet is a right side (the other side in the second direction). Thepaper thickness direction on the plane of the sheet is an up-downdirection (thickness direction, a third direction perpendicular to thefirst direction and the second direction), the near side on the plane ofthe sheet is an upper side (one side in the thickness direction, oneside in the third direction), and the far side on the plane of the sheetis a lower side (the other side in the thickness direction, the otherside in the third direction). To be specific, directions are inconformity with direction arrows described in each view. When viewedfrom the top, a direction in which a through hole, a gap region, or thelike extend long is referred to as a longitudinal direction, and adirection perpendicular to the longitudinal direction is referred to asa width direction. In FIGS. 1, 4, 6, 9, 10, and 11, the through hole ina board assembly sheet is shown with diagonal hatching.

First Embodiment

1. Board Assembly Sheet

A first embodiment of a board assembly sheet of the present invention isdescribed with reference to FIG. 1.

A board assembly sheet 1 (hereinafter, also referred to as a board sheet1) includes a plurality of mounting boards 4 to be described later, andas shown in FIG. 1, has a generally rectangular sheet shape(rectangle-shaped) extending in a plane direction when viewed from thetop. The board sheet 1 is defined by a mounting board region 2 and asurrounding region 3.

The mounting board region 2 is positioned at generally the center of theboard sheet 1 when viewed from the top, and is a region in which theplurality of (nine) mounting boards 4 are formed (defined). The mountingboard region 2 has a generally rectangular shape when viewed from thetop. In the mounting board region 2, the plurality of mounting boards 4are disposed in alignment in a grid pattern at spaced intervals to eachother in the front-rear direction and the right-left direction. That is,in the mounting board region 2, a gap region 5 in which the mountingboard 4 is not formed is formed between the plurality of mounting boards4 that are next to each other.

The mounting board 4 is a flexible wiring circuit board for mounting anelectronic component, and has a generally rectangular shape(rectangle-shaped) when viewed from the top. As described later, themounting board 4 includes a plurality of electronic component-connectingterminals 26, a plurality of external component-connecting terminals 27,and a plurality of wires 28.

The gap region 5 has a generally lattice shape when viewed from the top,and has a plurality of (two) first gap regions 6 extending in thefront-rear direction (longitudinal direction), and a plurality of (two)second gap regions 7 extending in the right-left direction (longitudinaldirection).

The plurality of first gap regions 6 are provided at spaced intervals toeach other in the right-left direction. The first gap region 6 is formedlinearly so as to be continuous from the front end edge (that is, afront end edge 16 c of the mounting board 4 that is positioned at thefrontmost side) to the rear end edge (that is, a rear end edge 16 d ofthe mounting board 4 that is positioned at the rearmost side) of themounting board region 2.

In the board sheet 1, one pair of through holes 12 (described later) areprovided corresponding to each of the first gap regions 6. That is, theone pair of through holes 12 are disposed in the surrounding region 3that is positioned at the outer side of each of the first gap regions 6.To be specific, one inner-side first through hole 13 a is formed in afront-side region 8 that is positioned at the front side of the onefirst gap region 6, and the other inner-side first through hole 13 a isformed in a rear-side region 9 that is positioned at the rear side ofthe first gap region 6.

The plurality of second gap regions 7 are provided at spaced intervalsto each other in the front-rear direction. The second gap region 7 isformed linearly so as to be continuous from the left end edge (that is,a left end edge 16 a of the mounting board 4 that is positioned at theleftmost side) to the right end edge (that is, a right end edge 16 b ofthe mounting board 4 that is positioned at the rightmost side) of themounting board region 2.

In the board sheet 1, the one pair of through holes 12 (described later)are provided corresponding to each of the second gap regions 7. That is,the one pair of through holes 12 are provided in the surrounding region3 that is positioned at the outer side of each of the second gap regions7. To be specific, one inner-side second through hole 14 a is formed ina left-side region 10 that is positioned at the left side of the onesecond gap region 7, and the other inner-side second through hole 14 ais formed in a right-side region 11 that is positioned at the right sideof the second gap region 7.

A width of the first gap region 6 and that of the second gap region 7(that is, a length in an orthogonal direction perpendicular to thelongitudinal direction of each of the gaps; a length in the right-leftdirection of the first gap region 6 and a length in the front-reardirection of the second gap region 7) are generally the same, and are,for example, 2000 μm or less, preferably 1500 μm or less, morepreferably 1000 μm or less, and for example, 10 μm or more, preferably30 μm or more.

The surrounding region 3 is around (that is, outer side in thefront-rear direction and outer side in the right-left direction of) themounting board region 2, and is a margin region positioned in aperipheral end portion of the board sheet 1. The surrounding region 3has a generally frame shape when viewed from the top in which the innershape and the outer shape thereof are a generally rectangular shape. Theinner peripheral edge of the surrounding region 3 is continuous to theouter peripheral edge of the mounting board region 2.

The surrounding region 3 includes the front-side region 8, the rear-sideregion 9, the left-side region 10, and the right-side region 11. Thefront-side region 8 is a region that is positioned at the from side ofthe mounting board region 2, and is formed from the front end edge ofthe mounting board region 2 to the front end edge of the board sheet 1in the front-rear direction. The rear-side region 9 is a region that ispositioned at the rear side of the mounting board region 2, and isformed from the rear end edge of the mounting board region 2 to the rearend edge of the board sheet 1 in the front-rear direction. The left-sideregion 10 is a region that is positioned at the left side of themounting board region 2, and is formed from the left end edge of themounting board region 2 to the left end edge of the board sheet 1 in theright-left direction. The right-side region 11 is a region that ispositioned at the right side of the mounting board region 2, and isformed from the right end edge of the mounting board region 2 to theright end edge of the board sheet 1 in the right-left direction. In fourcorners (front-left corner portion, front-right corner portion,rear-left corner portion, rear-right corner portion) of the surroundingregion 3, each of the regions (for example, the front-side region 8 andthe left-side region 10) is overlapped.

In the surrounding region 3, the plurality of through holes 12 areformed. The plurality of through holes 12 pass through the board sheet 1in the up-down direction, and include a plurality of (eight) firstthrough holes 13 and a plurality of (eight) second through holes 14.

The plurality of first through holes 13 have an elongated shape whenviewed from the top, and are formed linearly extending in the front-reardirection (longitudinal direction). The plurality of first through holes13 are disposed in the front-side region 8 and the rear-side region 9.To be specific, the plurality of (four) first through holes 13 aredisposed at spaced intervals to each other in the right-left directionin the front-side region 8. The plurality of (four) first through holes13 are disposed at spaced intervals to each other in the right-leftdirection in the rear-side region 9. The first through holes 13 disposedin the front-side region 8 are disposed so as to face the first throughholes 13 disposed in the rear-side region 9 with the mounting boardregion 2 sandwiched therebetween. That is, the four pairs of firstthrough holes 13 facing each other in the front-rear direction aredisposed.

The first through holes 13 are formed along phantom lines 15 (15 a and15 b) (that is, linear extending lines 15 formed by end edges 16 of themounting board 4) extending along the end edges 16 (the left end edge 16a and the right end edge 16 b) of the mounting board 4. That is, the endedges in the right-left direction (end edges in the width direction) ofthe first through holes 13 coincide with the phantom lines 15.

To be specific, of the plurality of first through holes 13, the twopairs of first through holes 13 (the inner-side first through holes 13a) disposed in the middle in the right-left direction are each formed tobe along both of the phantom line 15 b and the phantom line 15 a. Thephantom line 15 b extends along the right end edge 16 b of the mountingboard 4 a that is positioned at the left side in the two mounting boards4 (4 a and 4 b) that are next to each other in the right-left direction.The phantom line 15 a extends along the left end edge 16 a of themounting board 4 b that is positioned at the right side in the twomounting boards 4 (4 a and 4 b). That is, in the right-left direction(width direction), the inner-side first through hole 13 a is formed soas to be continuous from the phantom line 15 b extending along the rightend edge 16 b of the mounting board 4 a to the phantom line 15 a,extending along the left end edge 16 a, of the mounting board 4 b.

The two pairs of first through holes 13 (the outer-side first throughholes 13 b) disposed at the outer side in the right-left direction areeach formed so as to be along one of the phantom lines 15 (15 a or 15 b)extending along the left end edge 16 a or the right end edge 16 b of themounting board 4. That is, the one pair of outer-side first throughholes 13 b positioned at the leftmost side are formed so as to be alongthe phantom line 15 a extending along the left end edge 16 a of themounting board 4 positioned at the leftmost side (that is, the left endedge of the mounting board region 2). The one pair of outer-side firstthrough holes 13 b positioned at the rightmost side are formed so as tobe along the phantom line 15 b extending along the right end edge 16 bof the mounting board 4 positioned at the rightmost side (that is, theright end edge of the mounting board region 2).

The width (direction perpendicular to the longitudinal direction) of thefirst through hole 13 is generally the same as the distance (width ofthe first gap region 6) between the two mounting boards 4 next to eachother in the right-left direction.

As shown in FIG. 2B, in side cross-sectional view, the first throughhole 13 is formed so that end edges 17 of the first through hole 13facing each other in the front-rear direction along the end edges 16(the left end edge 16 a and the right end edge 16 b) gradually getcloser to each other in the up-down direction (thickness direction). Tobe specific, a front end edge 17 a and a rear end edge 17 b of the firstthrough hole 13 have a generally tapered shape when viewed in crosssection in which the distance therebetween decreases as it is closer tothe upper side. That is, the upper surface of the front end edge 17 a ofthe first through hole 13 is formed to be an acute angle toward theinner side of the first through hole 13, and the upper surface of therear end edge 17 b of the first through hole 13 is formed to be theacute angle toward the inner side of the first through hole 13.

As shown in FIG. 1, the plurality of second through holes 14 have anelongated shape when viewed from the top, and are formed linearlyextending in the right-left direction (longitudinal direction). Theplurality of second through holes 14 are disposed in the left-sideregion 10 and the right-side region 11. To be specific, the plurality of(four) second through holes 14 are disposed at spaced intervals to eachother in the front-rear direction in the left-side region 10. Theplurality of (four) second through holes 14 are disposed at spacedintervals to each other in the front-rear direction in the right-sideregion 11. The second through holes 14 disposed in the left-side region10 are disposed so as to face the second through holes 14 disposed inthe right-side region 11 with the mounting board region 2 sandwichedtherebetween. That is, the four pairs of second through holes 14 facingeach other in the right-left direction are disposed.

The second through holes 14 are formed along the phantom lines 15 (15 cand 15 d) extending along the end edges 16 (the front end edge 16 c andthe rear end edge 16 d) of the mounting board 4. That is, the end edgesin the width direction of the second through holes 14 coincide with thephantom lines 15.

To be specific, of the plurality of second through holes 14, the twopairs of second through holes 14 (the inner-side second through holes 14a) disposed in the middle in the front-rear direction are each formed soas to be along both of the phantom line 15 d and the phantom line 15 c.The phantom line 15 d extends along the rear end edge 16 d of themounting board 4 a that is positioned at the front side in the twomounting boards 4 (4 a and 4 c) that are next to each other in thefront-rear direction. The phantom line 15 c extends along the front endedge 16 c of the mounting board 4 c that is positioned at the rear sidein the two mounting boards 4 (4 a and 4 c). That is, in the front-reardirection, the inner-side second through hole 14 a is formed so as to becontinuous from the phantom line 15 d extending along the rear end edge16 d of the mounting board 4 a to the phantom line 15 c extending alongthe front end edge 16 c of the mounting board 4 c.

The two pairs of second through holes 14 (the outer-side second throughholes 14 b) disposed at the outer side in the front-rear direction areeach formed so as to be along one of the phantom lines 15 (15 c or 15 d)extending along the front end edge 16 c or the rear end edge 16 d of themounting board 4. That is, the one pair of outer-side second throughholes 14 b positioned at the frontmost side are formed so as to be alongthe phantom line 15 c extending along the front end edge 16 c of themounting board 4 positioned at the frontmost side (that is, the frontend edge of the mounting board region 2). The one pair of outer-sidesecond through holes 14 b positioned at the rearmost side are formed soas to be along the phantom line 15 d extending along the rear end edge16 d of the mounting board 4 positioned at the rearmost side (that is,the rear end edge of the mounting board region 2).

The width of the second through hole 14 is generally the same as thedistance in the front-rear direction (width of the second gap region 7)between the two mounting boards 4 next to each other in the front-reardirection.

As shown in FIG. 2A, in side cross-sectional view, the second throughhole 14 is formed so that end edges 18 of the second through hole 14facing each other in the right-left direction along the end edges 16(the front end edge 16 c and the rear end edge 16 d) gradually getcloser to each other in the up-down direction. To be specific, a leftend edge 18 a and a right end edge 18 b of the second through hole 14have a generally tapered shape when viewed in cross section in which thedistance therebetween decreases as it is closer to the upper side. Thatis, the upper surface of the left end edge 18 a of the second throughhole 14 is formed to be the acute angle toward the inner side of thesecond through hole 14, and the upper surface of the right end edge 18 bof the second through hole 14 is formed to be the acute angle toward theinner side of the second through hole 14.

The through hole 12 has a length L in the longitudinal direction (thelength in the front-rear direction of the first through hole 13, thelength in the right-left direction of the second through hole 14) of,for example, 1 mm or more, preferably 2 mm or more, and for example, 120mm or less, preferably 80 mm or less.

A width W (the length in an orthogonal direction perpendicular to thelongitudinal direction; the length in the right-left direction of thefirst through hole 13 and the length in the front-rear direction of thesecond through hole 14) of the through hole 12 is generally the same asthe width of the first gap region 6 or the second gap region 7, that is,generally the same as the distance between the two mounting boards 4next to each other. To be specific, the through hole 12 has a width Wof, for example, 2000 μm or less, preferably 1500 μm or less, morepreferably 1000 μm or less, and for example, 10 μm or more, preferably30 μm or more.

An aspect ratio (L/W) of the length L to the width W in the through hole12 is, for example, 1 or more, preferably 2 or more, more preferably 5or more, and for example, 3000 or less, preferably 500 or less, morepreferably 100 or less.

As shown in FIGS. 2A to 2B, the board sheet 1 includes a base insulatinglayer 20, a conductive pattern 21, and a cover insulating layer 22 inthis order in the up-down direction.

The base insulating layer 20 is disposed as the uppermost layer of theboard sheet 1. The base insulating layer 20 forms the outer shape of theboard sheet 1, and has a generally rectangular shape when viewed fromthe top extending in the plane direction. The upper surface of the baseinsulating layer 20 is formed flat. The base insulating layer 20 has aplurality of electronic component-connecting terminal opening portions23 and a plurality of external component-connecting terminal openingportions 24 in each of the mounting boards 4 in the mounting boardregion 2. The base insulating layer 20 has a plurality of firstsurrounding opening portions 25 in the surrounding region 3.

The plurality of electronic component-connecting terminal openingportions 23 are opening portions for allowing the electroniccomponent-connecting terminals 26 to expose to the upper surface side.The plurality of electronic component-connecting terminal openingportions 23 are disposed in alignment at spaced intervals to each otherso as to have a rectangular frame shape in generally the central portionof the mounting board 4. That is, the plurality of electroniccomponent-connecting terminal opening portions 23 are provided so as tocorrespond to a plurality of terminals 35 (described later) of anelectronic component to be mounted. Each of the electroniccomponent-connecting terminal opening portions 23 has a generallycircular shape when viewed from the top passing through the baseinsulating layer 20 in the up-down direction.

The plurality of external component-connecting terminal opening portions24 are opening portions for allowing the external component-connectingterminals 27 to expose to the upper surface side. The plurality ofexternal component-connecting terminal opening portions 24 are disposedin alignment at spaced intervals to each other in the width direction inthe front end portion of the mounting hoard 4. That is, the plurality ofexternal component-connecting terminal opening portions 24 are providedso as to correspond to a plurality of terminals of an external componentthat are electrically connected thereto. Each of the externalcomponent-connecting terminal opening portions 24 has a generallyrectangular shape (rectangle-shaped) when viewed from the top passingthrough the base insulating layer 20 in the up-down direction.

The plurality of first surrounding opening portions 25 are openingportions for forming the through holes 12 by communicating with secondsurrounding opening portions 29 of the cover insulating layer 22 to bedescribed later. The first surrounding opening portions 25 are formed inthe surrounding region 3 so as to correspond to the through holes 12.The first surrounding opening portion 25 has a generally tapered shapewhen viewed in cross section in which the width thereof decreases as itis closer to the upper side.

The base insulating layer 20 is formed from an insulating material.Examples of the insulating material include synthetic resins such aspolyimide resin, polyimide imide resin, acrylic resin, polyether nitrileresin, polyether sulfone resin, polyethylene terephthalate resin,polyethylene naphthalate resin, and polyvinyl chloride resin.Preferably, the base insulating layer 20 is formed from a polyimideresin.

The base insulating layer 20 has a thickness of, for example, 1 μm ormore, preferably 5 μm or more, and for example, 30 μm or less,preferably 10 μm or less, more preferably 8 μm or less.

The conductive pattern 21 is provided at the lower side of the baseinsulating layer 20 so as to be in contact with the lower surface of thebase insulating layer 20. The conductive pattern 21 includes theplurality of electronic component-connecting terminals 26, the pluralityof external component-connecting terminals 27, and the plurality ofwires 28 in each of the mounting boards 4 in the mounting board region2.

The plurality of electronic component-connecting terminals 26 areterminals for being electrically connected to the electronic componentsuch as imaging element 31 (described later). The plurality ofelectronic component-connecting terminals 26 are disposed in alignmentat spaced intervals to each other so as to have a generally rectangularframe shape in the central portion of the mounting hoard 4. That is, theelectronic component-connecting terminals 26 are disposed at the insideof the electronic component-connecting terminal opening portions 23.Each of the electronic component-connecting terminals 26 has a generallycircular shape when viewed from the top, and the upper surface thereofis exposed from the upper surface of the base insulating layer 20.

The plurality of external component-connecting terminals 27 areterminals for being electrically connected to the external component(not shown) such as mother board and power source. The plurality ofexternal component-connecting terminals 27 are disposed in alignment atspaced intervals to each other in the width direction in the front endportion of the mounting board 4. That is, the plurality of externalcomponent-connecting terminals 27 are disposed at the inside of theexternal component-connecting terminal opening portions 24. Each of theexternal component-connecting terminals 27 has a generally rectangularshape (rectangle-shaped) when viewed from the top, and the upper surfacethereof is exposed from the upper surface of the base insulating layer20.

The plurality of wires 28 are provided so as to correspond to theplurality of electronic component-connecting terminals 26 and theplurality of external component-connecting terminals 27. To be specific,the wires 28 are integrally formed with the plurality of electroniccomponent-connecting terminals 26 and the plurality of externalcomponent-connecting terminals 27 so as to connect them. That is, oneend of the wire 28 is continuous to the electronic component-connectingterminal 26, and the other end thereof is continuous to the externalcomponent-connecting terminal 27, so that the electroniccomponent-connecting terminal 26 is electrically connected to theexternal component-connecting terminal 27.

Examples of a material for the conductive pattern 21 include metalmaterials such as copper, silver, gold, and nickel, and an alloythereof, and solder. Preferably, copper is used.

In view of suppression of warping and handleability, the conductivepattern 21 (the wire 28) has a thickness (total thickness) of, forexample, 1 μm or more, preferably 3 μm or more, and for example, 15 μmor less, preferably 10 μm or less, more preferably 8 μm or less.

The wire 28 has a width of, for example, 5 μm or more, preferably 10 μmor more, and for example, 200 μm or less, preferably 100 μm or less,more preferably 50 μm or less.

The cover insulating layer is provided at the lower side of the baseinsulating layer 20 and the conductive pattern 21 so as to cover theconductive pattern 21. That is, the cover insulating layer 22 isdisposed so as to be in contact with the lower surface and the sidesurfaces of the conductive pattern 21 and a portion that is not coveredwith the conductive pattern 21 on the lower surface of the baseinsulating layer 20. An outer shape of the cover insulating layer 22 isformed so as to be generally the same as that of the base insulatinglayer 20. The cover insulating layer 22 has the plurality of secondsurrounding opening portions 29 in the surrounding region 3.

The plurality of second surrounding opening portions 29 are openingportions for forming the through holes 12 by communicating with thefirst surrounding opening portions 25 in the base insulating layer 20.The second surrounding opening portions 29 are formed in the surroundingregion 3 so as to correspond to the through holes 12. The secondsurrounding opening portion 29 has a generally tapered shape when viewedin cross section in which the width thereof decreases as it is closer tothe upper side.

The cover insulating layer 22 is formed from the same insulatingmaterial as that for the base insulating layer 20 described above.Preferably, the cover insulating layer 22 is formed from a polyimideresin.

The cover insulating layer 22 has a thickness of, for example, 1 μm ormore, preferably 2 μm or more, and for example, 30 μm or less,preferably 10 μm or less, more preferably 5 μm or less.

In the hoard sheet 1, the surface at the side in which the electroniccomponent-connecting terminals 26 are exposed, that is, the surface ofthe base insulating layer 20 is a mounting surface on which theelectronic component is mounted. The surface at the opposite side to themounting surface, that is, the surface of the cover insulating layer 22is a rear surface on which a temporary fixing sheet 41 (described later)is disposed.

In view of reduction in thickness, a total thickness (maximum thickness)of the board sheet 1, that is, a total thickness of the mounting board 4is, for example, 60 μm or less, preferably 40 μm or less, morepreferably 20 μm or less, further more preferably 10 μm or less, and forexample, 1 μm or more, preferably 5 μm or more.

2. Producing Method of Board Assembly Sheet

Next, a method for producing the board sheet 1 is described withreference to FIGS. 3A to 3E. The board sheet 1 can be, for example,produced by a metal supporting plate preparing step, a base insulatinglayer forming step, a conductive pattern forming step, a coverinsulating layer forming step, and a metal supporting plate removingstep.

As shown in FIG. 3A, in the metal supporting plate preparing step, ametal supporting plate 40 is prepared.

The metal supporting plate 40 is, for example, formed from metalmaterials such as stainless steel, 42-alloy, aluminum, and copper alloy.Preferably, the metal supporting plate 40 is formed from stainlesssteel.

The metal supporting plate 40 has a thickness of, for example, 5 μm ormore, preferably 10 μm or more, and for example, 50 μm or less,preferably 30 μm or less.

The upper surface of the metal supporting plate 40 is formed flat(smooth).

As shown in FIG. 3B, in the base insulating layer forming step, the baseinsulating layer 20 is formed on the upper surface of the metalsupporting plate 40. To be specific, the base insulating layer 20 havingthe opening portions (the electronic component-connecting terminalopening portion 23, the external component-connecting terminal openingportion 24, and the first surrounding opening portion is formed on theupper surface of the metal supporting plate 40.

To be specific, as a material for the base insulating layer 20, avarnish of a photosensitive insulating material (for example,photosensitive polyimide) is applied to the entire upper surface of themetal supporting plate 40 to be dried, thereby forming a base film (baseinsulating layer). Thereafter, the base film is exposed to light via aphotomask having a pattern corresponding to the opening portions (23,24, and 25). Thereafter, the base film is developed, and cured byheating as needed.

As shown in FIG. 3C, in the conductive pattern forming step, theconductive pattern 21 is formed on the upper surface of the baseinsulating layer 20. To be specific, the conductive pattern 21 is formedon the upper surface of the base insulating layer 20 and on portions inthe upper surface of the metal supporting plate 40 that are exposed atthe electronic component-connecting terminal opening portions 23 and theexternal component-connecting terminal opening portions 24.

Examples of a forming method of the conductive pattern 21 includeadditive method and subtractive method.

As shown in FIG. 3D, in the cover insulating layer forming step, thecover insulating layer 22 is formed on the upper surfaces of theconductive pattern 21 and the base insulating layer 20. To be specific,the cover insulating layer 22 is formed on the upper surface and theside surfaces of the conductive pattern 21, and a portion that is notcovered with the conductive pattern 21 on the upper surface of the baseinsulating layer 20.

The cover insulating layer 22 is formed so as to have the secondsurrounding opening portions 29 positioned corresponding to the firstsurrounding opening portions 25 in the base insulating layer 20. In thismanner, the through holes 12 passing through the board sheet 1 in theup-down direction are formed.

The forming method of cover insulating layer 22 is, for example, thesame as that of the base insulating layer 20.

In this manner, the board sheet 1 including the base insulating layer20, the conductive pattern 21, and the cover insulating layer 22 isobtained in a state of being supported by the metal supporting plate 40.

As shown in FIG. 3E, in the metal supporting plate removing step, themetal supporting plate 40 is removed.

Examples of a removing method include a method of peeling the metalsupporting plate 40 from the lower surface of the board sheet 1 and amethod of processing the metal supporting plate 40 by wet etching.

In this manner, the board sheet 1 including the base insulating layer20, the conductive pattern 21, and the cover insulating layer 22 isobtained. The produced board sheet 1 is reversed upside down, therebyobtaining the board sheet 1 shown in FIG. 1.

3. Singulation of Board Assembly Sheet

Next, a method for singulating the mounting boards 4 of the board sheet1 is described with reference to FIGS. 3F and 4. The board sheets 1 canbe, for example, singulated by a temporary fixing sheet disposing stepand a cutting step.

In the temporary fixing sheet disposing step, the board sheet 1 isdisposed in the temporary fixing sheet 41.

To be specific, the board sheet 1 is disposed on the upper surface ofthe temporary fixing sheet 41 so that the upper surface of the temporaryfixing sheet 41 is brought into contact with the entire rear surface(opposite side to the mounting surface: the cover insulating layer 22)of the board sheet 1.

The temporary fixing sheet 41 is a sheet that fixes the board sheet 1 soas to surely cut the board sheet 1 and can be peeled off from thesingulated mounting boards 4 after the cutting step. Examples of thetemporary fixing sheet 41 include dicing tapes such as slightlyadhesive-type dicing tape and ultraviolet ray peeling-type dicing tape.

In the cutting step, the board sheet 1 is cut to be formed into theplurality of mounting boards 4. That is, the board sheet 1 is dicedalong each of the outer shapes (the end edges 16 a to 16 d) of theplurality of mounting boards 4 by using a cutting blade of a cuttingdevice.

As the cutting blade, for example, a dicing blade 42 having a disk shapeand rotatable with respect to its axis is used. The width of the dicingblade 42 is generally the same as that of the through hole 12.

In the cutting method, first, the blade edge of the dicing blade 42 isdisposed so as to be along the longitudinal direction of the throughhole 12 and to be inserted into the through hole 12, and next, thedicing blade 42 is relatively moved toward the inner side of the boardsheet 1 (that is, along the gap region 5) to another through hole 12facing thereto with the mounting board region 2 sandwiched therebetween.

To be specific, in the cutting in the front-rear direction, the bladeedge of the dicing blade 42 is inserted into the first through hole 13in the front-side region 8, and next, the dicing blade 42 is relativelymoved in the front-rear direction with respect to the board sheet 1 fromthe first through hole 13 in the front-side region 8 to the firstthrough hole 13 in the rear-side region 9 along the first gap region 6on the phantom line 15. Meanwhile, in the cutting in the right-leftdirection, the blade edge of the dicing blade 42 is inserted into thesecond through hole 14 in the left-side region 10, and next, the dicingblade 42 is relatively moved in the right-left direction with respect tothe board sheet 1 from the second through hole 14 in the left-sideregion 10 to the second through hole 14 in the right-side region 11along the second gap region 7 on the phantom line 15.

At this time, immediately after the moving, the dicing blade 42gradually starts shaving the upper end of the end edge of the throughhole 12 (front end of the acute angle formed in the front end edge 17 aof the first through hole 13, front end of the acute angle formed in theleft end edge 18 a of the second through hole 14) in the board sheet 1,and thereafter, completely shaves the board sheet 1 in the up-downdirection.

As shown in FIG. 4, in this manner, a cutting through hole 45 obtainedby cutting in the cutting step is formed in a lattice shape in the boardsheet 1, and the plurality of mounting boards 4 are independent fromeach other.

Thereafter, the cut board sheet 1 is peeled from the temporary fixingsheet 41.

In this manner, the singulated plurality of mounting boards 4 areobtained. The mounting board 4 is a wiring circuit board for mountingthe electronic component (described later) such as the imaging element31, and does not include the electronic component yet.

The mounting board 4 is, for example, preferably used for the wiringcircuit board for mounting the imaging element 31 (described later).That is, the mounting board 4 is preferably used for an imaging devicesuch as camera module.

4. Mounted Device

As one example of a mounted device including the mounting board 4, animaging device 30 is described with reference to FIG. 5. The imagingdevice 30 includes the mounting hoard 4, the imaging element 31 as oneexample of an electronic component, a housing 32, an optical lens 33,and a filter 34.

The mounting board 4 is disposed so that the base insulating layer 20that is the mounting surface is defined as the upper side and the coverinsulating layer 22 is defined as the lower side.

The imaging element 31 is a semiconductor element that converts light toelectric signals, and examples thereof include solid imaging elementssuch as CMOS sensor and CCD sensor.

The imaging element 31 has a generally rectangular flat plate shape whenviewed from the top, and though not shown, includes a silicon such as Siboard, and a photo diode (photoelectric converting element) and a colorfilter that are disposed thereon. The plurality of terminals 35corresponding to the electronic component-connecting terminals 26 of themounting board 4 are provided on the lower surface of the imagingelement 31.

The imaging element 31 is mounted on the mounting board 4. That is, theterminal 35 of the imaging element 31 is flip-chip mounted on thecorresponding electronic component-connecting terminal (imagingelement-connecting terminal) 26 of the mounting board 4 via a solderbump 36 or the like. In this manner, the imaging element 31 is disposedin the central portion of the mounting board 4 to be electricallyconnected to the electronic component-connecting terminal 26 of themounting board 4.

The imaging element 31 is mounted on the mounting board 4 to constitutean imaging unit 37. That is, the imaging unit 37 includes the mountingboard 4 and the imaging element 31 that is mounted thereon.

The housing 32 is disposed in the central portion when viewed from thetop of the mounting board 4 so at to be spaced apart from and tosurround the imaging element 31 so as to surround it. The housing 32 hasa generally rectangular cylindrical shape when viewed from the top. Inthe upper end of the housing 32, a fixing portion for fixing the opticallens 33 is provided.

The optical lens 33 is disposed at the upper side of the mounting board4 at spaced intervals to the mounting board 4 and the imaging element31. The optical lens 33 has a generally circular shape when viewed fromthe top, and is fixed by the fixing portion so that light from theoutside reaches the imaging element 31.

The filter 34 is disposed between the imaging element 31 and the opticallens 33 at spaced intervals thereto, and fixed to the housing 32.

5. Function and Effect

The board sheet 1 is a board assembly sheet in which the plurality ofmounting hoards 4 are defined. The mounting hoard 4 has a totalthickness of 60 μm or less. The board sheet 1 has the through hole 13and the second through hole 14 passing through the board sheet 1 in theup-down direction. The first through hole 13 and the second through hole14 are formed so as to be along the phantom line 15 (linear extendingline formed by each of the end edges 16 a to 16 d) extending along theend edges 16 a to 16 d of the mounting board 4.

According to the board sheet 1, the dicing blade 42 is inserted intoeach of the first through holes 13 and the second through holes 14 atthe time of singulation, and next, the board sheet 1 can be cut from theside surface thereof along the gap region 5 on the end edge 16 or on thephantom line 15 in the mounting board 4. Thus, when the dicing blade 42is brought into contact with the board sheet 1, pressing of the dicingblade 42 toward the board sheet 1 in the up-down direction can beprevented. Accordingly, an impact or a distortion imparted to the entireboard sheet 1 can be reduced. Therefore, damage of the board sheet 1 andthe damage of the mounting board 4 can be reduced, and a yield of themounting board 4 can be improved. That is, the plurality of mountingboards 4 can be efficiently obtained.

Also, the first through hole 13 and the second through hole 14 areformed in advance, so that cutting dusts in the volume of the firstthrough hole 13 and the second through hole 14 can be reduced, andcontamination of the mounting board 4 can be suppressed.

In the board sheet 1, the mounting board 4 has a generally rectangularshape extending in the front-rear direction and the right-left directionwhen viewed from the top, and includes the first through hole 13extending in the front-rear direction and the second through hole 14extending in the right-left direction.

According to the board sheet 1, the impact or the distortion imparted tothe entire board sheet 1 can be reduced in both of the cuttings in thefront-rear direction and the right-left direction. Thus, the mountingboard 4 in a generally rectangular shape when viewed from the top can bemore surely obtained without damage.

In the board sheet 1, the first through hole 13 and the second throughhole 14 have a width of 2000 μm or less.

According to the board sheet 1, when the board sheet 1 is cut by usingthe dicing blade 42 having the same width as the width of the firstthrough hole 13 and the second through hole 14, the cutting area can bereduced. Thus, the cutting dusts can be reduced, and the contaminationof the mounting board 4 can be suppressed.

In the board sheet 1, the width of the first through hole 13 and thesecond through hole 14 is generally the same as the width of the firstgap region 6 and the second gap region 7.

According to the board sheet 1, the right end edge 16 b of the mountingboard 4 at the left side and the left end edge 16 a of the mountingboard 4 at the right side can be simultaneously cut by one cutting. Or,the rear end edge 16 d of the mounting board 4 at the front side and thefront end edge 16 c of the mounting board 4 at the rear side can besimultaneously cut. Thus, there is no need for cutting in each of theend edges, so that the number of cutting steps can be reduced.

In the board sheet 1, the end edges 17 of the first through hole 13facing each other in the front-rear direction gradually get closer toeach other as they go closer to the upper side (the side of the mountingsurface). The end edges 18 of the second through hole 14 facing eachother in the right-left direction gradually get closer to each other asthey go closer to the upper side (the side of the mounting surface).Thus, the dicing blade 42 can be gradually brought into contact with theacute angle of the upper ends of both end edges 17 and 18 of the firstthrough hole 13 and the second through hole 14 to be cut. Thus, theimpact imparted to the entire board sheet 1 can be furthermore reduced,and the damage of the board sheet 1 can be furthermore suppressed.

6. Modified Examples

(1) In the embodiment shown in FIG. 1, the board sheet 1 includes thebase insulating layer 20, the conductive pattern 21, and the coverinsulating layer 22. As shown in FIG. 6, the board sheet 1 may furtherinclude a reinforcement layer 43.

That is, as referred to FIG. 7, the board sheet 1 shown in FIG. 6includes the reinforcement layer 43, the base insulating layer 20, theconductive pattern 21, and the cover insulating layer

The reinforcement layer 43 is disposed on the upper surface of the baseinsulating layer 20. The reinforcement layer 43 is disposed in thesurrounding region 3 when viewed from the top. To be specific, thereinforcement layer 43 is disposed in each of the left-side region 10and the right-side region 11. The reinforcement layer 43 has a generallyrectangular shape when viewed from the top. The reinforcement layer 43is formed so as not to be overlapped with the through holes 12 (thefirst through holes 13) when projected in the up-down direction. Thatis, a cut-out portion 44 that protrudes outwardly from the inner-endedge in the right-left direction is formed in the reinforcement layer43.

In the embodiment shown in FIG. 6, a sag of the mounting board region 2can be suppressed, and handling properties of the board sheet 1 areimproved. As a result, the mounting boards 4 can be more accuratelysingulated, and the yield of the mounting board 4 can be improved.

(2) In the embodiment shown in FIG. 1, the board sheet 1 includes theone mounting board region 2. Alternatively, for example, though notshown, the board sheet 1 may include a plurality of (two or more)mounting board regions 2. That is, the plurality of mounting boardregions 2 may be also disposed in alignment in the front-rear directionor the right-left direction at wider spaced intervals (the surroundingregion 3) than the gap region 5 that is formed in the mounting boardregion 2.

(3) In the embodiment shown in FIG. 1, the board sheet 1 has a sheetshape (paper sheet) extending in the plane direction. Alternatively, forexample, as shown in FIG. 8, the board sheet 1 may be also a long-lengthsheet extending long in the front-rear direction. The board sheet 1shown in FIG. 8 is wound around into a roll shape.

In the board sheet 1 shown in FIG. 8, a plurality of regions includingthe mounting board region 2 and the surrounding region 3 correspondingthereto are continuous in a long-length direction.

In the embodiment shown in FIG. 8, the board sheet 1 extends long in thefront-rear direction. Alternatively, for example, though not shown, theboard sheet 1 may also extend long in the right-left direction.

(4) In the embodiment shown in FIG. 1, as referred to FIG. 2, each ofthe end edges 17 of the first through hole 13 and the end edges 18 ofthe second through hole 14 gradually gets closer to each other as eachof them goes closer to the upper side. That is, the through hole 12 hasa generally tapered shape when viewed in cross section. Alternatively,for example, though not shown, each of the end edges 17 of the firstthrough hole 13 and the end edges 18 of the second through hole 14 mayalso retain a certain distance in the up-down direction. That is, eachof the first through hole 13 and the second through hole 14 may alsohave a generally rectangular shape when viewed in cross section.

In the producing method of this embodiment, for example, the firstthrough hole 13 and the second through hole 14 can be also formed bylaser processing or the like.

(5) In the embodiment shown in FIG. 1, the through hole 12 are eachformed so as to be along the phantom line 15 in the surrounding region3. Alternatively, for example, though not shown, a through hole that isnot along the phantom line 15 may be also formed in addition to thethrough hole 12.

(6) In the embodiment shown in FIGS. 1 and 2A to 2B, the board sheet 1and the mounting board 4 include the base insulating layer 20, theconductive pattern 21, and the cover insulating layer 22. That is, theconductive layer (conductive pattern) of the board sheet 1 is a singlelayer. Alternatively, for example, though not shown, the conductivelayer of the board sheet 1 may be also a plurality of layers. That is,for example, the board sheet 1 may also include the base insulatinglayer 20, the conductive pattern 21, the cover insulating layer 22, thesecond conductive pattern, and the second cover insulating layer in thisorder in the up-down direction (structure of two layers of conductivelayer). Or, the board sheet 1 may also include the base insulating layer20, the conductive pattern 21, the cover insulating layer 22, the secondconductive pattern, the second cover insulating layer, the thirdconductive pattern, and the third cover insulating layer in this orderin the up-down direction (structure of three layers of conductivelayer).

The configuration of the second conductive pattern and the thirdconductive pattern is the same as that of the conductive pattern 21, andthe configuration of the second cover insulating layer and the thirdcover insulating layer is the same as that of the cover insulating layer22.

The total thickness of the mounting board 4 is the same (for example, 60μm or less) as that of the embodiment shown in FIG. 1.

The total thickness of the wire (for example, the total thickness of thewire 28 included in the conductive pattern 22, the wire included in thesecond conductive pattern, and the metal wire included in the thirdconductive pattern) is, in view of suppression of warping, for example,15 μm or less, preferably 10 μm or less, more preferably 8 μm or less,and in view of handleability, for example, 1 μm or more, preferably 3 μmor more.

Second Embodiment

The board sheet 1 of the second embodiment is described with referenceto FIG. 9. In the board sheet 1 of the second embodiment, the samereference numerals are provided for members corresponding to each ofthose in the above-described first embodiment, and their detaileddescription is omitted.

In the board sheet 1 of the second embodiment, the two pairs of throughholes 12 are provided corresponding to each of the gap regions 5.

That is, the two pairs of first through holes 13 are provided in thesurrounding region 3 that is positioned at the outer side of each of thefirst gap regions 6. To be specific, the two inner-side first throughholes 13 a are formed in the front-side region 8 that is positioned atthe front side of the one first gap region 6, and the two inner-sidefirst through holes 13 a are formed in the rear-side region 9 that ispositioned at the rear side of the first gap region 6.

The inner-side first through hole 13 a at the left side is formed so asto be along the phantom line 15 b extending along the right end edge 16b of the mounting board 4 a that is positioned at the left side. Thatis, the left end edge of the inner-side first through hole 13 a at theleft side coincides with the phantom line 15 b. Meanwhile, theinner-side first through hole 13 a at the right side is formed so as tobe along the phantom line 15 a extending along the left end edge 16 a ofthe mounting board 4 b that is positioned at the right side. That is,the right end edge of the inner-side first through hole 13 a at theright side coincides with the phantom line 15 a.

The two pairs of second through holes 14 are provided in the surroundingregion 3 that is positioned at the outer side of each of the second gapregions 7. To be specific, the two inner-side second through holes 14 aare formed in the left-side region 10 that is positioned at the leftside of the one second gap region 7, and the two inner-side secondthrough holes 14 a are formed in the right-side region 11 that ispositioned at the right side of the second gap region 7.

The inner-side second through hole 14 a at the front side is formed soas to be along the phantom line 15 d extending along the rear end edge16 d of the mounting board 4 a that is positioned at the front side.That is, the front end edge of the inner-side second through hole 14 aat the front side coincides with the phantom line 15 d. Meanwhile, theinner-side second through hole 14 a at the rear side is formed so as tobe along the phantom line 15 c extending along the front end edge 16 cof the mounting board 4 c that is positioned at the rear side. That is,the rear end edge of the inner-side second through hole 14 a at the rearside coincides with the phantom line 15 c.

In the board sheet 1, the blade edge of the dicing blade 42 is disposedso as to be along the longitudinal direction of each of the throughholes 12 and to be inserted into each of the through holes 12, and next,the dicing blade 42 is relatively moved to another through hole 12facing thereto with the mounting board region 2 sandwiched therebetween,so that the mounting boards 4 can be singulated.

In the board sheet 1 of the second embodiment, the same function andeffect as that of the board sheet 1 of the first embodiment can beachieved. In view of reduction of the number of cutting steps,preferably, the first embodiment is used.

In the modified example of the second embodiment, the same modifiedexample as that of the first embodiment can be applied.

Third Embodiment

Next, the board sheet 1 of a third embodiment is described withreference to FIG. 10. In the board sheet 1 of the third embodiment, thesame reference numerals are provided for members corresponding to eachof those in the above-described first to second embodiments, and theirdetailed description is omitted.

In the board sheet 1 of the third embodiment, the plurality of (24)through holes 12 are formed so as to be along a portion of the end edge16 of the mounting board 4.

To be specific, of the plurality of (12) first through holes 13, theplurality of (six) inner-side first through holes 13 a are formedbetween the mounting boards 4 that are next to each other. That is, theplurality of inner-side first through holes 13 a are formed in the firstgap region 6 of the mounting board region 2. The width of the inner-sidefirst through hole 13 a is generally the same as the distance in theright-left direction (width of the first gap region 6) between the twomounting boards 4 that are next to each other. That is, the inner-sidefirst through hole 13 a is continuous from the right end edge 16 h ofthe mounting board 4 a that is disposed at the left side to the left endedge 16 a of the mounting board 4 b that is disposed at the right side.

The plurality of (six) outer-side first through holes 13 b are formed soas to be next to the outer-side end edge (the left end edge or the rightend edge) of the mounting board region 2 in the surrounding region 3.The outer shape of the outer-side first through hole 13 b is the same asthat of the inner-side first through hole 13 a.

Of the plurality of (12) second through holes 14, the plurality of (six)inner-side second through holes 14 a that are disposed at the middle inthe front-rear direction are formed between the mounting boards 4 thatare next to each other. That is, the plurality of inner-side secondthrough holes 14 a are formed in the second gap region 7 of the mountingboard region 2. The width of the inner-side second through hole 14 a isgenerally the same as the distance in the front-rear direction (width ofthe second gap region 7) between the two mounting boards 4 that are nextto each other. That is, the inner-side second through hole 14 a iscontinuous from the rear end edge 16 d of the mounting board 4 a that isdisposed at the front side to the front end edge 16 c of the mountingboard 4 c that is disposed at the rear side.

The plurality of (six) outer-side second through holes 14 b are formedso as to be next to the outer-side end edge (the front end edge or therear end edge) of the mounting board region 2 in the surrounding region3. The outer shape of the outer-side second through hole 14 b is thesame as that of the inner-side second through hole 14 a.

In the third embodiment, the through holes 12 are formed such that eachof the end edges 16 (the left end edge 16 a, the right end edge 16 b,the front end edge 16 c, and the rear end edge 16 d) of each of themounting boards 4 are in contact with (next to) the through hole 12.That is, the first through holes 13 are formed such that the left endedge 16 a and the right end edge 16 b of each of the mounting boards 4are next to the through hole 13 therealong, and the second through holes14 are formed such that the front end edge 16 c and the rear end edge 16d of each of the mounting boards 4 are next to the through hole 14therealong.

In the board sheet 1 of the third embodiment, the same function andeffect as that of the board sheet 1 of the first embodiment can beachieved. In view of furthermore suppression of adhesion of the cullingdusts to the mounting board 4, preferably, the third embodiment is used.That is, in the board sheet 1 of the third embodiment, the through hole12 is formed in advance around the mounting board 4, so that the cuttingdusts corresponding to the through hole 12 can be reduced around themounting board 4 (the gap region) at the time of cutting. Therefore, theadhesion of the cutting dusts to the mounting board 4 can be suppressed.

In the modified example of the third embodiment, the same modifiedexample as that of the first embodiment can be applied.

Fourth Embodiment

Next, the board sheet 1 of a fourth embodiment is described withreference to FIGS. 11 and 12. In the board sheet 1 of the fourthembodiment, the same reference numerals are provided for memberscorresponding to each of those in the above-described first to thirdembodiments, and their detailed description is omitted.

In the board sheet 1 of the fourth embodiment, the through hole 12 isformed so as to be along the entire end edges 16 of the mounting boards4.

In the fourth embodiment, the through hole 12 is formed in the entirefirst gap regions 6 and the entire second gap regions 7, and thesurrounding region 3 next to the mounting board region 2.

The through hole 12 has a generally lattice shape when viewed from thetop. That is, the through hole 12 includes the plurality of (four) firstthrough holes 13 and the plurality of (four) second through holes 14,and they are perpendicular to each other.

The plurality of first through holes 13 are disposed at spaced intervalsto each other in the right-left direction. The first through holes 13are continuous from the rear end portion of the front-side region 8 tothe front end portion of the rear-side region 9.

The plurality of second through holes 14 are disposed at spacedintervals to each other in the front-rear direction. The second throughholes 14 are continuous from the right end portion of the left-sideregion 10 to the left end portion of the right-side region 11.

In the board sheet 1, the plurality of (nine) mounting boards 4 areindependent from each other by the through hole 12, and are alsoindependent from the surrounding region 3.

In the board sheet 1 of the fourth embodiment, a supporting layer 50disposed at the lower side of the board sheet 1 is provided.

The supporting layer 50 supports the plurality of mounting boards 4 andthe surrounding region 3. The outer shape of the supporting layer 50 hasgenerally the same shape as that of the board sheet 1.

Examples of the supporting layer 50 include release films made ofpolyethylene terephthalate (PET) film, polyethylene film, polypropylenefilm, paper, or the like, and the above-described dicing tapes.

The board sheet 1 of the fourth embodiment can be, for example, producedby the metal supporting plate preparing step, the base insulating layerforming step, the conductive pattern forming step, the cover insulatinglayer forming step, a supporting layer disposing step, and the metalsupporting plate removing step.

The metal supporting plate preparing step, the base insulating layerforming step, the conductive pattern forming step, and the coverinsulating layer forming step are the same as those of the firstembodiment.

In this manner, the board sheet 1 including the base insulating layer20, the conductive pattern 21, and the cover insulating layer 22 isobtained in a state of being supported by the metal supporting plate 40.

In the supporting layer disposing step, the supporting layer 50 isdisposed on the surface of the cover insulating layer 22 of the boardsheet 1.

Lastly, the metal supporting plate removing step is carried out. Themetal supporting plate removing step is the same as that of the firstembodiment.

In this manner, the board sheet 1 is obtained in a state of beingsupported by the supporting layer 50.

In the board sheet 1 of the fourth embodiment, the same function andeffect as that of the board sheet 1 of the first embodiment can beachieved. In the board sheet 1 of the fourth embodiment, in particular,the through hole 12 is formed so as to be along the entire end edges 16of the mounting boards 4. Thus, each of the plurality of mounting boards4 is independent, so that the mounting board 4 can be peeled from thesupporting layer 50 without cutting the board sheet 1 at the time ofsingulation. Accordingly, the damage of the mounting board 4 can bereduced, and the yield of the mounting board 4 can be improved. That is,the plurality of mounting boards 4 can be efficiently obtained.

Also, the through holes 12 are formed in advance, and there is no needfor culling, so that the cutting dusts generated by cutting can besurely suppressed, and the contamination of the mounting board 4 can besuppressed.

In the modified example of the fourth embodiment, the same modifiedexample as that of the first embodiment can be applied. The board sheet1 of the fourth embodiment is wound around into a roll shape in a stateof being supported by the supporting layer 50 as shown in FIG. 12.Although not shown, the end edge 17 of the first through hole 13 and theend edge 18 of the second through hole 14 may gradually get closer toeach other as they go closer to the upper side as described withreference to FIG. 2.

The first to the fourth embodiments and the modified examples may beused in combination. For example, the through holes shown in FIG. 10 maybe provided in addition to the through holes 12 shown in FIG. 1.

While the illustrative embodiments of the present invention are providedin the above description, such is for illustrative purpose only and itis not to be construed as limiting the scope of the present invention.Modification and variation of the present invention that will be obviousto those skilled in the art is to be covered by the following claims.

INDUSTRIAL APPLICABILITY

The board assembly sheet of the present invention can be applied invarious industrial products, and for example, can be preferably used forimaging devices such as camera modules.

DESCRIPTION OF REFERENCE NUMERALS

1 Board assembly sheet

4 Mounting board

12 Through hole

13 First through hole

14 Second through hole

15 Phantom line

16 End edge

The invention claimed is:
 1. A board assembly sheet comprising amounting board region having a plurality of mounting boards each formounting an electronic component, the mounting boards being defined inthe board assembly sheet, and a surrounding region having a generallyframe shape when viewed from the top and having an exposed outerperipheral edge, and said surrounding region having an inner peripheraledge that is joined in a continuous and uninterrupted manner to an outerperipheral edge of the mounting board region such that there are nothrough holes disposed along the outer peripheral edge of the mountingboard region, wherein each of the mounting boards has a total thicknessof 60 μm or less, the board assembly sheet has at least one through holepassing through the board assembly sheet in a thickness direction, andthe at least one through hole is formed at least in the surroundingregion to be along a phantom line extending along an end edge of atleast one of the mounting boards.
 2. The board assembly sheet accordingto claim 1, wherein each of the mounting boards has a generallyrectangular shape when viewed from the top extending in a firstdirection and a second direction perpendicular to the first direction,and the at least one through hole includes a first through holeextending in the first direction and a second through hole extending inthe second direction.
 3. The board assembly sheet according to claim 1,wherein a length of the at least one through hole in an orthogonaldirection perpendicular to a direction along the end edge is 2000 μm orless.
 4. The board assembly sheet according to claim 3, wherein thelength of the at least one through hole in the orthogonal direction isgenerally the same as a distance between two mounting boards disposednext to each other in the orthogonal direction.
 5. The board assemblysheet according to claim 1, wherein the at least one through hole hasend edges facing each other in a direction along the end edge and whichgradually get closer to each other in the thickness direction.
 6. Theboard assembly sheet according to claim 1, wherein the at least onethrough hole includes a further through hole that is formed between twomounting boards disposed next to each other.